As an optical sensor, a bolometer type infrared sensor for detecting infrared rays has conventionally been known. The bolometer type infrared sensor is an optical sensor which detects infrared rays by using a material whose resistance value changes depending on temperature and disclosed in Patent Literature 1, for example. Patent Literature 1 discloses a bolometer type infrared sensor comprising a bolometer element for sensing an infrared ray incident thereon and a reference element for detecting a temperature change caused by a change in an environment in use. By using a signal issued from the bolometer element and a signal issued from the reference element, the bolometer type infrared sensor computes a signal which is free from the influence of the temperature change generated by the change in the environment in use, thereby detecting the infrared ray.